The present invention relates to a high performance filter element. The filter element according to the present invention is particularly useful as the principal component in an automotive lube oil filter assembly.
The performance of filter elements for use in automotive lube oil filter assemblies is evaluated based on a number of parameters. These include (1) the grams of test dust that can be filtered per pound of filter material, (2) the grams of test dust that can be filtered by a given filter cartridge and (3) the weight average efficiency of the filter material. The weight average efficiency (WAE) is the percentage of suspended solids retained by the filter material relative to total solids suspended in the fluid filtered. Parameter (2) above is often simply called the "capacity" of the filter cartridge.
It will be appreciated that the ideal filter will deliver both high efficiency and high capacity, but that these typically are competing parameters. That is, the higher a filter's efficiency, the sooner it will become clogged and thus the lower its capacity. Conversely, the higher a filter's capacity, the coarser it must be to enjoy a long life without clogging, and thus the more particulate that will pass through. Nonetheless, it is possible to design filter elements that have both higher capacity and higher efficiency than competing products. In this regard, however, it is very difficult to predict in advance what combinations of materials, processing conditions and physical characteristics will deliver a filter element having particularly advantageous performance parameters.
Hydroentangling is a process for producing nonwoven fabrics by impinging a plurality of fine columnar streams of water onto a fibrous web carried by an apertured or patterned conveying means. There is thus produced a felt-like material in which even relatively short fibers can be mechanically intertwined without the damaging effects of needling. One example of a patent describing hydroentangling is U.S. Pat. No. 3,485,706, the disclosure of which is hereby expressly incorporated by reference, to the extent not inconsistent herewith. In this patent, an apertured hydroentangled fabric is produced wherein the apertures in the fabric correspond to knuckles in the wire screen used to support and convey the fibrous web. Patterned supporting means are disclosed for imparting to the resulting hydroentangled fabric a desired ornamental appearance.
Similarly, U.S. Pat. No. 2,862,251 discloses the formation of a hydroentangled/apertured gauze-like web (col. 10, lines 17-25). At column 37, line 59 of this patent, it is suggested that the products produced thereby may be useful as filter materials.
U.S. Pat. No. 4,612,237 applies hydroentangling technology to produce filter media. Specifically, this patent discloses a hydroentangled felt comprising a uniformly dispersed sheet-like structure containing poly(tetrafluoroethylene) fibers and glass fibers hydraulically entangled onto a supporting scrim.